[InstSimplify] Match 1.0 and 0.0 for both operands in SimplifyFMAMul

Because we do not constant fold multiplications in SimplifyFMAMul,
we match 1.0 and 0.0 for both operands, as multiplying by them
is guaranteed to produce an exact result (if it is allowed to do so).

Note that it is not enough to just swap the operands to ensure a
constant is on the RHS, as we want to also cover the case with
2 constants.

Reviewers: lebedev.ri, spatel, reames, scanon

Reviewed By: lebedev.ri, reames

Differential Revision: https://reviews.llvm.org/D67553

llvm-svn: 372915

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 4ae052eb14b..dd477fe1c5d 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4582,10 +4582,18 @@ static Value *SimplifyFMAFMul(Value *Op0, Value *Op1, FastMathFlags FMF,
   if (match(Op1, m_FPOne()))
     return Op0;
 
+  // fmul 1.0, X ==> X
+  if (match(Op0, m_FPOne()))
+    return Op1;
+
   // fmul nnan nsz X, 0 ==> 0
   if (FMF.noNaNs() && FMF.noSignedZeros() && match(Op1, m_AnyZeroFP()))
     return ConstantFP::getNullValue(Op0->getType());
 
+  // fmul nnan nsz 0, X ==> 0
+  if (FMF.noNaNs() && FMF.noSignedZeros() && match(Op0, m_AnyZeroFP()))
+    return ConstantFP::getNullValue(Op1->getType());
+
   // sqrt(X) * sqrt(X) --> X, if we can:
   // 1. Remove the intermediate rounding (reassociate).
   // 2. Ignore non-zero negative numbers because sqrt would produce NAN.